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  1. #1
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    Disc brake question

    I recently upgraded from V-brakes to Avid BB7 disc brakes and the front feels a little under powered. Is it normal for a set of disc brakes which have identical rotors, levers, and calipers to feel stronger in the rear than the front? Do I need to move up to a 185 mm rotor up front? I weigh in at 210-215 clothed. For what it's worth, I only have 10 bike path miles on these brakes so far...really wishing my trails would dry. I don't even know if they're fully bedded in yet.

  2. #2
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    IT is going to be easier to lock up the rear wheel and "feel" like it has more power than the front.

    Otherwise, make sure the front one is set up correctly if you feel like it is underpowered compared to the rear. A 160mm rotor should be able to stop you quickly with the BB brakes.When I had BB5's, I never would pull the front brakes to hard as they were quite powerful if set up right.

    -Brett

  3. #3
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    Thanks Brett.
    I've got good pad to disc contact on both sides. Pretty sure they're set up correctly. In fact, I thought they were a piece of cake to set up compared to some of comments I've seen about them. Perhaps the front disc or pads are contaminated. I tried to keep my fingers off as best I could, but...

  4. #4
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    There is a chance some contamination occurred. Try cleaning it off with alcohol and rebed the pads by doing some heavy braking.

    -Brett

  5. #5
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    That's worth a try.

  6. #6
    Trail Tire TV on blogger
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    well when new they aren't quite as good as after a break in period, but after a few rides that should have set in. The front shouldn't lock up and will keep rolling when applying the brake as there is more forward force on it and as you apply the front brake more and more weight is forced on it from all your body/bike weight being forced against it

    Are you using the Speed dial levers? might have the things turned in way too far?
    Going to try and bring Trail Tire TV back. go take a look... http://trailtiretv.blogspot.com/

  7. #7
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    Quote Originally Posted by Pedro S
    I recently upgraded from V-brakes to Avid BB7 disc brakes and the front feels a little under powered. Is it normal for a set of disc brakes which have identical rotors, levers, and calipers to feel stronger in the rear than the front? Do I need to move up to a 185 mm rotor up front? I weigh in at 210-215 clothed. For what it's worth, I only have 10 bike path miles on these brakes so far...really wishing my trails would dry. I don't even know if they're fully bedded in yet.
    If you've only got 10 miles on the brakes they haven't even begun to break in. They will get better. Depending on how you ride and your braking technique it will take some time to bed the pads in. The process involves the burnishing of the rotor by the pads and the deposit of pad material on the brake rotor. This happens over time with use. It also tends to happen rather slowly so you may not notice it immediately. It will likely take several good rides to bed them in. Also, as has been noted, the front may still not feel as powerful as the rear due to the forward weight shift that occurs during braking. However in most cases you should be able to lock up the front, not that you'd want to, after the brakes are broken in. If after the break in you still don't feel you have enough up front then going to a 185mm front rotor will help a bunch. I'm 230lbs and have BB7s on both of my bikes. Both have a 185 on the front as the 160mm rotor simply doesn't provide enough power and heat resistance to be effective on down hills etc. At 215lbs a 185 front rotor might not be a bad idea for you, depending on your trails and riding style. But do give you brakes a chance to break in before you decide.

    Good Dirt
    "I do whatever my Rice Cripsies tell me to!"

  8. #8
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    I gave the front rotor a good wipe down with alcohol just in case it got contaminated during install. I do realize this reset the bedding in process of it. I live in the flat lands of the midwest so the only reason I would need a larger rotor is due to my weight and not from any big hills on my local trails. I'll take the advice and give it several rides before consider a move to a bigger rotor.

  9. #9
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    I'm at the point where I don't know which way to go with the front rotor size.

    To rule out the possibility of contamination, I sanded the front rotor and pads, cleaned them with alcohol and re-bedded properly. I have a few more rides on them now and they have gotten better. That said, I can only describe the front brake as adequate in performance but it still feels a little under powered to me. While I am looking for a little more power, I don't want to go to far with it and make it grabby or so strong that it would easily throw me over the bars. How big of a difference would going to a 185mm up front be?

  10. #10
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    A 185mm rotor will make a very noticeable difference up front. It will also tend to better balance the brakes. A larger front rotor and smaller rear is a very common practice in everything from bikes to automobiles. It helps to prevent rear wheel lock up during braking, yet still provides strong braking performance.

    I've found that a 185/160 combination evens out the lever pull nicely as well. You don't have to pull harder on the front brake than you do the rear. In the automotive industry this is accomplished not only with larger front rotors but also with metering valves and electronic brake force distributions systems, antilock brake systems, etc. Unfortunately with a bicycle that isn't practical. The closest we can get is running different rotor sizes front and rear.

    Anyway, at your weight I'd say devinately try a 185mm front rotor. I think you'll be pleasantly surprised at the improvement once the rotor is bedded in.

    Good Dirt
    "I do whatever my Rice Cripsies tell me to!"

  11. #11
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    Thanks Squash, I think I will give a 185mm rotor a try.

    Do I have to match a new rotor with new pads? I would think my existing pads would be just fine.

  12. #12
    Bicyclochondriac.
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    What cables and housing are you using? Same front and back?
    15mm is a second-best solution to a problem that was already solved.

  13. #13
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    Quote Originally Posted by kapusta
    What cables and housing are you using? Same front and back?
    Jagwire Ripcord front and back.

  14. #14
    Bicyclochondriac.
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    Quote Originally Posted by Pedro S
    Jagwire Ripcord front and back.
    Well, that rules out the cable/housing as a cause.
    15mm is a second-best solution to a problem that was already solved.

  15. #15
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    Looks like I'll be staying with the 160mm rotor for a while.

    My junk pogo stick RST fork won't take anything larger. In fact I don't think it can handle disc brakes at all. On a short little street ride around the neighborhood this afternoon I felt a vibration in the front while slowing to walking speed. As I looked down the left side of the fork with the brake applied, I could see it flexing back and forth causing the vibration. At higher speeds, the left side just flexes back and stays back when the front brake is applied until I slow to walking speed then it flexes back and forth again. I don't think this is normal or very safe.

    Now I'm in the market for a decent fork that won't cost more than the bike is worth.

  16. #16
    turtles make me hot
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    Ebay is your friend here. And definitely go with the 185 up front.
    I run a 185 rear and 203 up front, but I weigh a ton.
    I like turtles

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